Are metals in the muscle tissue of Mozambique tilapia a threat to human health? A case study of two impoundments in the Olifants River, Limpopo province, South Africa

Abstract

-Rural communities in South Africa are becoming increasingly reliant on freshwater fish to supplement their dietary protein requirement. Rising costs of other protein sources, increasing rural poverty and escalating rural populations are resulting in increasing consumption of fish from contaminated river systems. The Olifants River, Limpopo Basin, Eastern South Africa, has been systemically impaired and is now one of the most polluted rivers in South Africa. We measured the concentrations of metals in fish muscle tissue from two impoundments in the Olifants River (Flag Boshielo Dam and the Phalaborwa Barrage) and conducted a human health risk assessment following Heath et al., (2004) to investigate whether consumption of Oreochromis mossambicus from these impoundments posed a risk to the health of rural communities. Our results show that metals are accumulating in the muscle tissue of O. mossambicus even though the populations appear to be healthy. No patterns were observed in the ratios of the metals accumulated in the muscle tissue of O. mossambicus at each impoundment. The human health risk assessment identified that lead, antimony and chromium at Flag Boshielo Dam and lead at the Phalaborwa Barrage were above acceptable levels for the safe consumption based on a weekly 150 g fish meal. We conclude that consuming O. mossambicus from these impoundments could pose an unacceptable risk to the health of rural communities.

Metal contamination and human health risk associated with the consumption ofLabeo rosaefrom the Olifants River system, South Africa

“…The trend of metal concentrations found in the present study confirmed those of previous studies, which showed elevated concentration of Ba, Zn, B, Al, Cu and Fe in the muscle tissues of O. mossambicus and C. gariepinus (Kotze et al 1999;Addo-Bediako et al 2014a;Jooste et al 2015), L. rosae (Jooste et al 2014), Labeo umbratus Smith, 1841 (Coetzee et al 2002) and S. intermedius (Addo-Bediako et al 2014b) in the Olifants River system. The present study found a significant variation in the size of fish from each impoundment.…”

“…Analyses of metals were restricted to 10 metals: aluminium (Al), antimony (Sb), barium (Ba), boron (B), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), strontium (Sr) and zinc (Zn). These metals were selected due to their significant increases recorded over the past decade in the water, sediment and fish tissues from the Olifants River system (Coetzee et al 2002;Addo-Bediako et al 2014a, 2014bJooste et al 2014Jooste et al , 2015. A composite sediment sample consisting of five grab samples was collected from each of the three sites at Flag Boshielo Dam and from two sites at Loskop Dam in May 2011 using a Friedlinger mudgrab.…”

“…There is now a growing concern regarding the long-term impact of water pollution on the aquatic ecosystem and the health of rural communities, especially those still reliant on untreated water and aquatic resources from the Olifants River and its impoundments (Oberholster et al 2010(Oberholster et al , 2012. For example, the muscle tissues of four fish species from Flag Boshielo Dam were found to be contaminated with metals, including lead, antimony, chromium and cobalt, at concentrations exceeding acceptable levels for safe long-term consumption by humans (Addo-Bediako et al 2014a, 2014bJooste et al 2014Jooste et al , 2015 dams and evaluated the potential risk to human health posed by consuming fish, using a desk-top risk assessment protocol developed by the USEPA (2000). Relationships between metal concentrations in the water and sediment with those in the fish muscle tissue were explored.…”

“…Loskop Dam has been described as a repository for pollutants from the upper catchment of the Olifants River system (Oberholster et al 2010). Studies have shown elevated concentrations of metals in fish from Loskop Dam (Kotze et al 1999;Avenant-Oldewage and Marx 2000;Nussey et al 2000), Flag Boshielo Dam (Addo-Bediako et al 2014a, 2014bJooste et al 2014Jooste et al , 2015, and at Phalaborwa Barrage (Addo-Bediako et al 2014a, 2014bJooste et al 2014Jooste et al , 2015.…”

Gill net catch composition and catch per unit effort in Flag Boshielo Dam, Limpopo Province, South Africa

“…An important consideration prior to developing a fishery in Flag Boshielo Dam is the potential human health risks associated with the consumption of fish from the Olifants River System. Concentrations of heavy metals that could severely impair human health were found in muscle tissue of S. intermedius (Addo-Bediako et al, 2014b;Marr et al, 2015), O. mossambicus (Addo-Bediako et al, 2014a), L. rosae (Jooste et al, 2014;Lebepe et al, 2016) and C. gariepinus (Jooste et al, 2015;Marr et al, 2015) sampled from Flag Boshielo Dam. For this reason, the development of a fishery might be inappropriate even if catch rates are conducive to fisheries development.…”